1. Field of the Invention
The present invention relates to a circuit and method for compensating for an electrode motion artifact in which the electrode motion artifact is generated because impedance between a subject and a measuring electrode changes during measurement of the subject's biosignal, and the electrode motion artifact can be differentially measured and an electrocardiogram signal can be adjusted by introducing a predetermined voltage Vc or an electric current Vi into the subject.
2. Description of Related Art
A biometric measurement device can collect and analyze a minute action current, an electrical change of the action current, and the like. An action current is generated within a subject, such as from the heart of a human body. A biometric measurement device can indicate various biometric information about a corresponding subject in forms that a predetermined medical examiner can recognize. The biometric measurement device connects an electrode and a subject that is a target for medical test and interprets the change of a voltage measured by the electrode to collect a biosignal.
In this case, the biometric measurement device has to physically contact the electrode on the surface of the subject to collect a biosignal. Accordingly, the change of impedance between the subject and the electrode inevitably occurs because of the characteristics in which the subject continually moves and the problem in which the electrode misses a predetermined measurement point.
The change of impedance may function as noise, such as an electrode motion artifact, with respect to biosignals collected in the biometric measurement device. Accordingly, the change of impedance may distort a waveform with respect to measurement results or interfere with measurement of generated information.
The most obvious case of the electrode motion artifact described above is when the attachment of an electrode is faulty. As an example of a configuration for recognizing the fault, U.S. Pat. No. 5,632,280 (hereinafter, referred to as ‘conventional art’) discloses a circuit monitoring whether the attachment of the electrode is faulty by using an amplifier having a gain of one and a voltage source. It is illustrated in FIG. 1.
FIG. 1 is a diagram illustrating monitoring with respect to a faulty attachment of an electrode in the conventional art.
As illustrated in FIG. 1, uni-directional electric current Ip is supplied to a plurality of electrodes in the conventional art. In the conventional art, output signal Vi may be calculated by ‘Vi=Vprobe+Ip*(Rf1+Rf2+Rp)+Ip*(Z1+Z2)’. Also, an impedance component between electrodes and skin is measured by ‘Z1+Z2’. Accordingly, it is possible to monitor whether the attachment of an electrode is a fault by using the change of the impedance component ‘Z1+Z2’.
However, since a biosignal is differentially measured, an impedance component substantially contained in the biosignal, such as a component of electrode motion artifact, may be defined by the impedance difference between electrodes, such as Z1−Z2. Accordingly, the electrode motion artifact has to be removed. However, a method of measuring impedance component ‘Z1+Z2’ may not remove electrode motion artifact ‘Z1−Z2’ from the differentially measured biosignal.